#include <fstream>
#include <algorithm>
#include <iomanip>
#define x first
#define y second
using namespace std;

ifstream in("infasuratoare.in");
ofstream out("infasuratoare.out");

pair <double,double> v[125005];
int n,minim;
double ymin;
vector <pair<double,double>> sol;


double arie(pair <double,double> a,pair <double,double> b,pair <double,double> c)
{
   return a.x*(b.y - c.y) + b.x * (c.y - a.y) + c.x * (a.y- b.y);
}

inline bool cmp(pair <double,double> a,pair <double,double> b)
{
    if(arie(v[1],a,b)>0)
        return 1;
    return 0;
}

int main()
{
    in>>n;
    in>>v[1].x>>v[1].y;
    ymin = v[1].y;
    minim = 1;
    for(int i=2;i<=n;i++)
        {
            in>>v[i].x>>v[i].y;
            if ((v[i].y < ymin) || (ymin == v[i].y && v[i].x < v[minim].x))
                {
                    ymin = v[i].y;
                    minim = i;
                }
        }

    swap(v[minim],v[1]);
    sort(v+2,v+n+1,cmp);


    sol.push_back(v[1]);
    sol.push_back(v[2]);
    sol.push_back(v[3]);

    for(int i=4;i<=n;i++)
    {
        while(arie(sol[sol.size()-2],sol.back(),v[i]) < 0)
                sol.pop_back();
        sol.push_back(v[i]);
    }
    out<<sol.size()<<'\n';
    for(int i=0;i<sol.size();i++)
        out<<setprecision(16)<<sol[i].x<<" "<<sol[i].y<<'\n';
    return 0;
}